Tomographic Problems in the Diagnostics of Fuel Cell Stacks

Hirschfeld, Julian

Diploma Thesis

Tomographic Problems in the Diagnostics of Fuel Cell Stacks

Hirschfeld, J. (Corresponding author)FZJ*

2009
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Berichte des Forschungszentrums Jülich 4291, V, 105 p. (2009) = Diploma Thesis, 2009

Please use a persistent id in citations: http://hdl.handle.net/2128/3588

Report No.: Juel-4291

Abstract: A novel scheme for detecting inhomogeneous internal currents in a fuel cell stack is suggested. Plates of high conductivity, including small parallel slits, are placed between each fuel cell in a stack. These may consist of aluminum. In this diploma thesis the scheme is investigated for the case that the flowfield plates in use consist of graphite. Whenever a local inhomogeneity in the current density of a particular cell occurs, currents in the adjacent metal plates emerge to compensate the diff.erence to the next cell's current density distribution. Due to the slits in the metal plates, these currents are enforced to the surface of the stack, where they can be detected more easily. Further e.ffects of the metal plates are first, the high conductivity of the small plates completely prevents the inhomogeneities from spreading to neighboring cells. And secondly, even at the particular cell the inhomogeneity is distributed equally over the undamaged area of the cell. Thus this scheme leads to much better diagnostic possibilities and at the same time reduces electric instabilities to an extent where they probable become harmless. This scheme will be explained .first in a simple model to clarify the idea. But very precise 3 dimensional computations using realistic parameters, representing real fuel cell materials, are presented corroborating the results of the simple model. On the basis of the measured surface currents, information about anomalies of the currents in the MEA can be obtained by using the methods of tomography. Unfortunately tomography alone does not lead to unique results in this case. But when assuming plausible defect structures one can exclude improbable de.ficiencies by applying a special form of simulated annealing. In this way most defects can be localized and their extent be determined.

Note: Record converted from VDB: 12.11.2012
Note: Diploma Thesis, 2009

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